1. Field of the Invention
The present invention relates generally to infusion devices. More particularly, the invention concerns an elastomeric bladder type infusion device and cooperating reservoir fill assembly. The infusion device of the invention is used for delivering a beneficial agent to a patient at a substantially constant rate.
2. Discussion of the Prior Art
A number of infusion pumps embodying an elastomeric balloon or bladder for delivery of a quantity of pharmaceutically active material to a patient have been suggested in the past. For example U.S. Pat. No. 4,915,693 issued to Hessel discloses an infusion pump comprising an elastomeric bladder having at least an open end and an elongated stress member extending concentrically within the entire length of the hollow portion of the bladder and having a fluid tight seal therewith. Both a filling port and an exit port are provided in the stress member, each in fluid communication with the interior of the bladder by way of an influent and an effluent lumen respectively. The stress member has a diameter that is greater than the relaxed internal diameter of the bladder, and has a length that exceeds the relaxed internal length of the hollow portion of the bladder so that it prestresses the bladder in both the axial and radial directions, when disposed therein, substantially filling the bladder in its unfilled state. The Hessel device also includes a one-way valve in the stress member which permits flow in the influent lumen only in the direction of the interior of the bladder.
Another type of balloon infusion devise is disclosed in U.S. Pat. No. 4,386,929 issued to Perry et al. The Perry et al device has spaced apart inlet and outlet means and the bladder, which is capable of expanding and contracting radially and axially upon inflation and deflation. When deflated, the lumen of the bladder is substantially completely filled by lumen filling means which protect the bladder from being punctured by the hypodermic needle used to fill and inflate the bladder. The lumen filling means resists the compressive load applied during insertion of the needle and maintains the inlet and outlet means in spaced apart relationship while providing substantially no resistance to the axial expansion of the bladder. By having the lumen of the bladder filled with the lumen filling means when the bladder is deflated before its subsequent inflation and deflation, substantially complete expulsion of the fluid contents of the bladder can be obtained.
Very early balloon type devices are described in U.S. Pat. Nos. 3,468,308 and 3,469,578 issued to Bierman. These patents describe a device for expelling a liquid from a bladder member at an extremely slow rate over an extended period of time. In the device described in U.S. Pat. No. 3,469,578, the liquid is expelled slowly by pressure induced on the liquid by the internal stresses of the distended bladder member. In the device disclosed in U.S. Pat. No. 3,468,308, the liquid is expelled by pressure control means which controls pressure applied to the exterior of the bladder member to control its rate of collapse.
In the devices described in both of the aforementioned patents, the bladder member comprises a balloon, or tube-like member which is typically distendable both length wise and laterally when initially pressured. Admission and discharge of liquid is of necessity through a single neck, or outlet portion of the balloon-like bladder.
Among the more unique infusion devices ever developed are those described in U.S. Pat. Nos. 5,163,940 and 4,354,278 which were issued to the present inventor. Still another novel prior art infusion device is described in U.S. Pat. No. 5,700,244 which patent was also issued to the present inventor. Because the apparatus of the present invention constitutes an improvement over the apparatus described in the U.S. Pat. No. 5,700,244, this latter patent is hereby incorporated by reference as though fully set forth herein.